1. Field of the Invention
The subject invention generally pertains to PTAC refrigerant systems that include an electric heater and a blower. The invention more specifically pertains to a way of attenuating the whistle that tends to emanate from an area near the electric heater.
2. Description of Related Art
Packaged Terminal Air Conditioners/Heat Pumps or PTACs, as they are known in the HVAC industry, are self-contained refrigerant systems with an electric heater for selective heating and cooling modes. Although PTACs are often used for cooling and heating hotel rooms, they are also used in a wide variety of other commercial and residential applications such as apartments, hospitals, nursing homes, schools, and government buildings. PTACs are usually installed in an opening of a building's outer wall, so an exterior-facing refrigerant coil can exchange heat with the outside air. In some cases, the refrigerant side of the system is a heat pump that not only provides cooling, but also provides heat during milder conditions or contributes heat when the electric heater is operating.
Because PTACs protrude into the living space of a room, they need to be as compact and quiet as possible. The electric heater, refrigerant circuit, fans, and other components of the system are all tightly packaged within a minimally sized housing. This presents a number of challenging problems, particularly with the electric heater.
The heater, of course, can get quite hot, so it needs to be safely spaced apart from the exterior walls of the PTAC's housing. To avoid wasting heat, the heater should also be isolated from the exterior-facing refrigerant coil, which is cold during the heating mode for absorbing heat from the outside air. Consequently, the electric heater is typically installed immediately upstream of the indoor fan, which circulates the room air and/or some ventilating outside air through the PTAC.
With the electric heater at this location, the current inventors have discovered that a “whistling” noise seems to emanate from the heater. Supporting the heating elements or other components more firmly or less firmly failed to eliminate the whistle. Since the noise disappears when the heater is de-energized (while the indoor fan is still running) the true source of the noise was a mystery. After closely studying the problem, however, the current inventors have discovered the true source of the noise and now propose a solution.